ofxDualTouch

Dual-zone multi-touch trackpad input for openFrameworks on macOS.

GLFW/OF do not deliver raw trackpad touch events on macOS, so this addon bridges AppKit's NSTouch API directly into OF. Two optional zones (left/right half of the window) each track the first finger that touches them, with easing back to a centre point and click-to-lock behaviour, plus a turnkey controller that wires it all together.

Requirements

• macOS only for trackpad capture (AppKit NSTouch). Other platforms build fine

via a stub; isAvailable() reports false.

• openFrameworks 0.12+ (uses glm).

Quick start (turnkey)

#include "ofxDualTouch.h"

class ofApp : public ofBaseApp {
	ofxDualTouchController dualTouch;
	void setup() override { dualTouch.setup(); }
	void update() override { dualTouch.update(ofGetLastFrameTime()); }
	void mousePressed(int x, int y, int button) override { dualTouch.handleMousePressed(x, y, button); }
};

The controller owns a capture and two ofxDualTouchZones:

• Left zone centre: (width split / 2, height / 2)
• Right zone centre: (width (0.5 + split / 2), height / 2)

Call setup() again in windowResized() — it is idempotent and re-swizzles the touch methods and recomputes zone centres.

Raw capture (events + polling)

ofxDualTouchCapture capture;

capture.setup();                                  // must run after the OF window exists
ofAddListener(capture.touchDown, this, &ofApp::onTouchDown);
// ... capture.touchMoved, capture.touchUp with void onTouch...(ofxDualTouchPoint & p)

for (auto & t : capture.getTouches()) {           // polling works too
	ofDrawCircle(t.pos.x, t.pos.y, 10);
}

ofxDualTouchPoint { int id; glm::vec2 pos; } — pos is in window pixels, y-down (already flipped from AppKit's bottom-left origin).

Zones

ofxDualTouchZone implements first-finger-wins tracking plus return-to-centre:

• touchDown / touchMoved / touchUp feed it raw points; a zone only accepts the

touch it owns.

• On release the circle eases back to its centre over lerpDuration seconds

using the current easing function.

• toggleLock() / isLocked(): a click turns return-to-centre off; the circle

stays where you leave it (and locks again anywhere you drag it).

• setLerpDuration(float), setEasing(ofxDualTouchEasingType), setCentre(glm::vec2).
• Getters: getPosition(), getTarget(), getCentre(), getTrail(),

isTouching(), isLerping(), getLerpProgress().

Eight easings are provided in ofxDualTouchEasing.h (default EASE_OUT_QUAD), as enum, names, and std::function table.

Examples

• example-ofxDualTouchZone (inside this addon) — the full dual-zone prototype

built on ofxDualTouchController (split, lock, easings, keys). Build with make Release (or make RunRelease) from addons/ofxDualTouch/example-ofxDualTouchZone.

• examples/input_output/ofxDualTouchExample — minimal raw capture: touch

circles, finger count, event logging.

• examples/input_output/ofxDualTouchZoneExample — same dual-zone prototype as

a top-level OF example.

How it works

ofxDualTouchCapture::setup() finds the OF window (ofGetCocoaWindow()) and uses class_replaceMethod to substitute the content view's touchesBegan/Moved/Ended/CancelledWithEvent: implementations. Touches are normalized from NSTouch.normalizedPosition to window pixels, the Y axis is flipped, and each NSTouch.identity is mapped to a sequential integer id that is released when the finger lifts.

Note: class_replaceMethod swizzles the view's class directly. If you swizzle
a different GL view class, only the same class is affected.

License

MIT, see license.md.